1. Filed of the Invention
The present invention relates to telecommunications testing. More particularly, the present invention relates to systems and methods for visualizing bit errors occurring in telecommunication access networks.
2. Background
Today's widespread growth in deployment of higher speed DSL service, such as ADSU2/2+, enables telecom service providers to offer voice, video and data over a single twisted pair of copper wires. This is often termed the “triple play” of the telecommunications industry, and more particularly of the digital telecommunications industry.
For the successful adoption of triple play services, telecom providers must meet or exceed the quality of service expected by customers. Quality of service can be impacted by many technical problems. One common problem is the existence of faults in the copper pair that create faults in the ADSL signal, which lead to lost packets and transmission delays. These lost packets and delays create slow data rates and degrade the quality of voice and video service.
The same concerns are also applicable to other telecom services, beyond ADSL service, including ISDN service, and even service provided over fiber optic cable.
No matter what the physical network is composed of, telecom service providers must routinely test and qualify their networks to ensure the quality of service that customers demand in the marketplace.
When analyzing a digital network, one common performance metric is the measurement of bit error rate (BER). This metric is often measured by devices known as bit error rate testers (BERTs), which are designed specifically to test digital networks, systems and subsystems. Generally speaking, the rate of bits incorrectly conveyed over a network is a measure of the bit error rate (BER) of that network, and is an indication of the performance and operability of the network. Typically, some sort of predetermined test pattern that is broken up into a stream of IP packets is sent through the network and a suitable BERT compares the received pattern with a stored version of the test pattern. The BERT itself may also be capable of generating the test pattern, sending the test pattern out over the network, and receiving back the stream of data that it has sent out.
One well-known BERT is the HST-3000 available from JDS Uniphase (San Jose, Calif.). This device is a handheld, modular platform for copper and multi-service testing. The device includes an LCD display that is operable to display various menus and network performance data. As part of its functionality, the HST-3000 includes set-top-box (STB) emulation that enables the HST-3000 to establish program streams in a terminate mode not requiring customer premises equipment (CPE). Quality of Service (QoS) parameter measurement along with detailed troubleshooting analysis features make the HST-3000 a particularly advanced video tool.
Despite the availability of BERTs generally, and the relatively advanced HST-3000 in particular, there is nevertheless a need to further improve upon digital network analysis tools.
For example, testing video services delivered over various access network technologies (DSL, FTTx, etc.) present a complex environment to a field technician. While it is possible to analyze the quality of a video transport stream by analyzing its corresponding digital data, there can be no subjective evaluation without decoding the “picture” for human evaluation. However, a decode process for a full motion video program on a portable field test tool would be very expensive and difficult to accomplish, especially on a typical small screen graphical user interface (GUI) display employed on a device like the HST-3000. Furthermore, “hide” algorithms in a typical video decoder hide various error conditions such as lost video data that would result in lost pixels on the television (monitor) screen.
Thus, there is a need for an improved portable digital video tester that can not only provide objective analysis of a video stream, but can also provide a means for enabling a subjective analysis of the video.